Tactile feedback for indicating validity of communication link with an implantable medical device

ABSTRACT

Implantable medical device telemetry is provided between an implantable medical device and an external communication device. The implantable medical device includes a device transmitter and/or a device receiver. The external communication device includes a moveable communication head including an antenna therein connected to at least one of an external transmitter and/or an external receiver for communication with the device transmitter and/or the device receiver of the implantable medical device. A user moves the moveable head apparatus relative to the implantable medical device. Tactile feedback is provided to the user via the moveable head apparatus upon movement of the moveable head apparatus to a position where valid telemetry can be performed.

CROSS-REFERENCE TO RELATED APPLICATION

This application is a continuation application of U.S. patentapplication Ser. No. 10/612,860, filed Jul. 3, 2003 entitled “TactileFeedback for Indicating Validity of Communication Link with anImplantable Medical Device”, which is a continuation of priorapplication Ser. No. 09/430,708, filed Oct. 29, 2000, entitled “TactileFeedback for Indicating Validity of Communication Link with anImplantable Medical Device”, now granted as U.S. Pat. No. 6,644,321.

FIELD OF THE INVENTION

The present invention relates to communication links with implantablemedical devices. More particularly, the present invention pertains totechniques for indicating that such communication links are valid.

BACKGROUND OF THE INVENTION

In the field of implantable medical devices, such as cardiac pacemakers,tachyarrhythmia control devices, implantable drug dispensing devices,monitoring devices, and nerve stimulators, it has become common toprovide a transceiver system for performing functions such as the remoteprogramming and the telemetering of data out of the implanted device.For example, in such devices, it has become desirable to have theability to reprogram the device's modes of operation, parameters, andother functions and/or to monitor the performance of such devices, bothhistorically and contemporaneously. Generally, such implantable medicaldevices are designed to provide two-way telemetry by radio frequencysignal transmission between the implanted medical device and aprogramming head or wand of an external communication device, e.g.,external programmer apparatus, to provide for the exchange of codedtransmitted information therebetween.

As the complexity of implantable medical devices increases over time,telemetry systems for enabling such implantable devices to communicatewith external communication devices, e.g., programmers, has become moreimportant. For example, it is desirable for a user, e.g., a physician,to noninvasively exercise some amount of control over the implantablemedical device, e.g., to turn the device on or off after implantation,to adjust various parameters of the implantable medical device afterimplantation, etc.

Further, as implantable medical devices include more advanced features,it is typically necessary to convey correspondingly more information tothe implantable medical device relating to the selection and control ofsuch advanced features. For example, if a pacemaker is selectivelyoperable in various pacing modes, it is desirable that a physician beable to noninvasively select a mode of operation. Further, for example,if a pacemaker is capable of pacing at various rates, or of deliveringstimulating pulses of varying energy levels, it is desirable that thephysician be able to select, on a patient-by-patient basis, appropriatevalues for such variable operational parameters.

Not only has the complexity of implantable medical devices led to theneed to convey correspondingly more information to the implantablemedical device, but it has also become desirable to enable the implantedmedical device to communicate information outside of the patient to anexternal communication device, e.g., programmer. For example, fordiagnostic purposes, it is desirable for the implanted device to be ableto communicate information regarding its operational status to thephysician. Various implantable medical devices are available which cantransmit such information to an external communication device, e.g., thetransmission of a digitized ECG signal for display, storage, and/oranalysis by the external communication device.

As used herein, the term “uplink” and “uplink telemetry” will be used todenote the communications channel for conveying information from theimplanted medical device to an external communication device, e.g., aprogrammer. Conversely, the term “downlink” and “downlink telemetry”will be used to denote the communications channel for conveyinginformation from an external communication device to the implantedmedical device.

Various telemetry systems for providing the necessary communicationchannels between an external communication device and an implantedmedical device have been described. For example, typically, telemetrysystems are employed in conjunction with an externalprogrammer/processing unit. A programmer for noninvasively programming acardiac pacemaker is described in the following U.S. patents toHartlaub, et al., each commonly assigned to the assignee of the presentinvention: U.S. Pat. No. 4,250,884, entitled “Apparatus for and Methodof Programming the Minimum Energy Threshold for Pacing Pulses to beApplied to a Patient's Heart;” U.S. Pat. No. 4,273,132, entitled“Digital Cardiac Pacemaker with Threshold Margin Check;” U.S. Pat. No.4,273,133, entitled “Programmable Digital Cardiac Pacemaker with Meansto Override Effects of Reed Switch Closure;” U.S. Pat. No. 4,233,985,entitled “Multi-Mode Programmable Digital Cardiac Pacemaker;” U.S. Pat.No. 4,253,466, entitled “Temporary and Permanent Programmable DigitalCardiac Pacemaker;” and U.S. Pat. No. 4,401,120, entitled “DigitalCardiac Pacemaker with Program Acceptance Indicator.” Aspects of theprogrammer that are the subject of the foregoing Hartlaub et al. patentsare described in U.S. Pat. No. 4,208,008 to Smith, entitled “PacingGenerator Programming Apparatus Including Error Detection Means,” and inU.S. Pat. No. 4,236,524 to Powell et al., entitled “Program TestingApparatus.”

Most commonly, telemetry systems for implantable medical devices employa radio frequency (RF) transmitter and receiver in the implantablemedical device, and a corresponding RF transmitter and receiver in theexternal communication device, e.g., programming unit. Within theimplantable medical device, the transmitter and receiver use an antennafor receiving downlink telemetry signals and for radiating RF signalsfor uplink telemetry. For example, the radiating RF signals may bemagnetically coupled through inductive (antenna) coils.

To communicate digital data using RF telemetry, a digital encodingscheme such as described in U.S. Pat. No. 5,127,404 to Wyborny et al.,entitled “Improved Telemetry Format,” is used. In particular, forexample, in downlink telemetry a pulse interval modulation scheme may beemployed wherein the external communication device, e.g., programmer,transmits a series of short RF “bursts” or pulses in which the durationof an interval between successive pulses, e.g., the interval from thetrailing edge of one pulse to the trailing edge of the next pulse,encodes the data. For example, a shorter interval may encode a “0” bitwhile a longer interval may encode a “1” bit.

The external communication devices, e.g., programming devices, typicallyinterface with the implanted medical device through the use of aprogramming head or paddle. For example, generally, the programming heador paddle is a hand-held unit adapted to be placed on or near thepatient's body over the implant site of the patient's implanted medicaldevice. The programming head may effect closure of a reed switch in theimplantable medical device using a magnet to initiate a telemetrysession. Thereafter, uplink and downlink communication may take placebetween the implanted medical device's transmitter/receiver and thereceiver/transmitter of the external communication device. Other methodsof initiating a telemetry session may also be used. For example, awake-up pulse from an external communication device may be used towake-up the implanted medical device, which polls its downlink receiverat an appropriate interval.

For programming arrangements, and/or for monitoring arrangements, bothuplink and downlink telemetry signal strength vary as a function ofprogramming head positioning relative to the implantable device. Inother words, the signal strength varies as a function of the coefficientof coupling between the communication head, e.g., programming headincluding an antenna configuration, and the implanted device. Therefore,it is important for the programming head to be properly positioned overthe patient's implant site so that downlink RF signals can be detectedin the implantable medical device and uplink signals can be detected bythe programming head of the external communication device. For example,if the programming head is too far away from the implantable medicaldevice, the attenuation of RF signals transmitted across the boundary ofthe patient's skin may be too great, preventing a telemetry link frombeing established.

As such, with appropriate feedback to a user, the user can position andreposition the programming head over the implant site until a suitableposition is located to a establish a valid communication link betweenthe external communication device and the implanted medical device.Various feedback techniques have been used to indicate to a user when aprogramming head has been properly located over a patient's implantedmedical device to establish a valid telemetry link.

For example, one technique used for determining when the programminghead is properly positioned can be characterized as an “open loop”technique in that the determination of the correct head positioning isbased solely upon an assessment of whether the uplink signal (i.e., thesignal transmitted from the implanted medical device to the externalcommunication device) meets some minimum requirement. In such an openloop verification system, adequate downlink signal strength is nottested. For example, an open loop system for determining the properpositioning of a programming head is described in U.S. Pat. No.4,531,523 to Anderson, entitled “Digital Gain Control for the Receptionof Telemetry Signals from Implanted Medical Devices.”

A communication protocol using handshaking can also be used to verifythat a minimum downlink field strength for detection in the implantedmedical device exists to signal a physician that correct headpositioning has been achieved. However, conventional handshakingprotocols do not provide any information useable for optimization ofhead positioning to ensure an adequate operating margin. In other words,proper programming head positioning may be indicated even though theprogramming head is actually marginally positioned, such that a veryslight shift in positioning (e.g., due to patient motion) results indownlink telemetry failure.

Further, closed loop systems have also been described for providingfeedback to a user for positioning of the communication head forattaining a valid communication link with an implanted medical device.For example, in U.S. Pat. No. 5,324,315 to Grevious, entitled“Closed-Loop Downlink Telemetry and Method for Implantable MedicalDevice,” a specific type of downlink telemetry pulse is transmitted fromthe external communication device to the implanted medical device. Inparticular, the downlink pulses are bursts having a linear rampingenvelope. The characteristics of the downlink burst envelope are suchthat the amplitude of the signal as detected by the implanted medicaldevice's receiver, relative to the receiver's detection threshold, canbe ascertained by measuring the time that the detected burst exceeds thereceiver's detection threshold. This information can be communicated tothe external communication device. In response to receipt of suchinformation regarding the relative strength of the detected downlinksignals, the external communication device can modulate the peakamplitude of the downlink burst envelopes by modulating the gain of theexternal communication device transmitter. As such, the externalcommunication device can then ensure an adequate margin over theimplanted medical device's detection threshold while at the same timeavoiding the transmission of unnecessarily high energy downlink signals.As described therein, the downlink signal strength and/or the uplinksignal strength can be used for activation of a telemetry statusindication.

Generally, as described in U.S. Pat. No. 5,324,315, the provision offeedback as to the proper positioning of a programming head with respectto an implanted antenna of an implanted medical device includes the useof a position indicator, for example, an audible tone generator and/or avisible indicator such as a light emitting diode (LED). When signalstrength and accuracy are confirmed (e.g., with parity checking, errorchecking codes, and the like), programmer control circuitry will causethe position indicator to indicate that a link has been established. Ifadequate signal strength and content accuracy cannot be confirmed, theposition indicator will so indicate.

Further, U.S. Pat. No. 5,107,833 to Barsness, entitled “Telemetry GainAdjustment Algorithm and Signal Strength Indication in a NoisyEnvironment,” describes provision of a signal strength indicator forproviding the user with a visual alpha-numeric readout of signalstrength during establishment of a telemetry link. The signal strengthis derived from an automatic gain control factor of an adjustable gainamplification stage of an external communication device, e.g., theadjustable gain amplification stage of the uplink receiver of aprogrammer which receives its input signals from an RF programming headhaving an antenna configuration therein. The gain of the uplink receiveris a function of the strength of the uplink signal. As describedtherein, with a telemetry session initiated and uplink signal lossoccurring for performing telemetry, the automatic gain controlalgorithms scan through gain levels searching for one, which will resultin valid uplink detection. A displayed range of signal strengthscorrespond to the scaled automatic gain control levels or factors. Sincethe automatic gain control value is lowest for maximum signal level andhighest for minimum signal level, the value is complemented for use as asignal strength indicator to the user. As described therein, variouslevels of automatic gain control could be used. For example, scaledvalues of 0-100, or values of 0-9, may be used for display to a userattempting to position the programming head. The signal strengthindicator may appear on a screen of a programmer or it could appear onthe programming head as a numeric display for the user to view as theuser attempts to find an optimum position for the programmer head basedon the viewed strength signal indication.

Further, programmer heads available under the trade designation9766/9766A/9767, available from Medtronic, Inc., assignee of the presentinvention, provide for a multiple LED array display for providingindication of proper positioning of the programmer head. The array isdriven as a function of the uplink signal strength. The signal strengthis determined as a function of the gain of the uplink receiver. Acertain number of LEDs of the LED array are activated based upon thesignal strength. For example, when the head is not at an optimumposition, only one LED may be lit. As the programmer head is movedaround the site of the implanted medical device, more LEDs may be litindicating more optimal positions. Further, no LEDs of the array may belit until valid telemetry can be accomplished, i.e., as determined by ahandshake process.

As described above, conventional RF heads incorporate various types ofindicators to guide placement of the RF head. For example, the 9766family of RF heads available from Medtronic Inc., assignee of thepresent invention, incorporate signal strength indicator LEDs to guideplacement of the RF head. Further, other positioning techniques haveused numerical displays for indicating the signal strength to a user toguide placement of the RF programmer head. However, in brightly litrooms, LEDs or visual numerical displays are sometimes difficult to seeand/or read. As such, these indicators are inadequate for optimalplacement of an RF programmer head.

Further, in some circumstances, implantable medical devices areimplanted in various regions of the body, which prohibit the viewing ofan RF programmer head as it is placed over the implant site. Forexample, neurostimulators are sometimes implanted in the hip area. Assuch, when a programming head of an external communication device isplaced for performing telemetry over the implant site, the user of thehead may find it difficult to view LEDs on the head.

SUMMARY OF THE INVENTION

The present invention provides for the use of tactile feedback inconjunction with the positioning of a communication head for performingtelemetry between an implantable medical device and an externalcommunication device. Tactile feedback allows a user to locate animplanted device with a communication head without looking at anindicator light, a numeric display, etc.

An implantable medical device telemetry method according to the presentinvention includes providing an implantable medical device and anexternal communication device. The implantable medical device includes adevice transmitter and/or a device receiver. The external communicationdevice includes an external transmitter and/or an external receiverconnected to an antenna for communication with the device transmitterand/or the device receiver. The method further includes determiningvalidity of a communication link between the device transmitter and/orthe device receiver of the implantable medical device and the externaltransmitter and/or the external receiver of the external communicationdevice. Tactile indication is provided as a function of the validitydetermination.

In one embodiment of the method, the external communication deviceincludes a user communication head moveable relative to the implantablemedical device when the implantable medical device is implanted. Thetactile indication is provided to a user via the user communicationhead.

In another embodiment of the method, the validity of the communicationlink is determined by detecting communication of a signal between theimplantable medical device and the external communication device. Thestrength of the communicated signal is determined and the strength ofthe communicated signal is compared to at least one predeterminedreference strength.

Further, with regard to this embodiment, a tactile indication may beprovided by controlling the frequency of vibration of the tactileindication as a function of the strength of the communicated signal.

In another embodiment of the method, determining the validity of acommunication link includes completing a handshake between the devicetransmitter and/or the device receiver of the implantable medical deviceand the external transmitter and/or the external receiver of theexternal communication device.

In yet another embodiment of the method, providing the tactileindication as a function of the validity determination may includeinitiation of the tactile indication upon determination of a validcommunication link. Further, with regard to this particular embodiment,the tactile indication may be discontinued after a predetermined timefollowing initiation thereof. Yet further, activation of an indicatormay be provided when the valid communication link becomes invalidfollowing such discontinuation of the tactile indication.

In yet another embodiment, the tactile indication as a function of thevalidity determination is provided by continuously providing tactileindication during the entire period of time that a valid communicationlink is determined.

Another implantable medical device telemetry method according to thepresent invention includes providing an implantable medical device andan external communication device. The implantable medical deviceincludes a device transmitter and/or a device receiver. The externalcommunication device includes a moveable head apparatus including atleast an antenna therein connected to at least one of an externaltransmitter and/or an external receiver for communication with thedevice transmitter and/or the device receiver of the implantable medicaldevice. The method further includes moving, by the user, the moveablehead apparatus relative to the implantable medical device. Tactileindication is provided to the user via the moveable head apparatus uponmovement of the moveable head apparatus to a position where informationbetween the device transmitter and/or the device receiver of theimplantable medical device and the external transmitter and/or externalreceiver of the external communication device is communicated.

An implantable medical device telemetry system is also describedaccording to the present invention. The system includes an implantablemedical device including a device transmitter and/or a device receiverand an external communication device. The external communication deviceincludes an external receiver and/or an external transmitter connectedto an antenna for communication with the device transmitter and/or thedevice receiver. The external communication device further includes atactile feedback generation device and control circuitry operable toinitiate the tactile feedback generation device as a function of thevalidity of a communication link between the implantable medical deviceand the external communication device.

In one embodiment of this system, the external communication deviceincludes a user communication head moveable relative to the implantablemedical device when the implantable medical device is implanted.Further, the tactile feedback generation device and the antenna of theexternal communication device are provided within the moveable usercommunication head.

In various embodiments of the system, the tactile feedback generationdevice may include a vibrating motor, a piezoelectric device, anelectric solenoid, or a relay contact.

A communication device for establishing a communication link with animplantable medical device is also described. The device includes anexternal receiver and/or an external transmitter connected to an antennafor communication with a device transmitter and/or a device receiver ofthe implantable medical device. The communication device furtherincludes a tactile feedback generation device and control circuitryoperable to initiate the tactile feedback generation device as afunction of the validity of a communication link between the implantablemedical device and the external communication device.

The above summary of the present invention is not intended to describeeach embodiment or every implementation of the present invention.Advantages, together with a more complete understanding of theinvention, will become apparent and appreciated by referring to thefollowing detailed description and claims taken in conjunction with theaccompanying drawings.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 is a diagram illustrating an implantable medical device in a bodyfor communication with an external communication device, wherein theimplantable medical device and external communication device providetelemetry with use of tactile feedback according to the presentinvention.

FIG. 2 is a general block diagram of circuitry of an implantable medicaldevice including transmitter and receiver circuitry according to thepresent invention.

FIG. 3 is a general block diagram of an illustrative telemetry systemusing tactile feedback according to the present invention.

FIG. 4 is one embodiment of a portion of the illustrative externalcommunication device shown generally in FIG. 3 according to the presentinvention.

FIG. 5 is a more detailed diagram of one illustrative embodiment of aportion of the external communication device shown in FIG. 4 accordingto the present invention.

FIG. 6 is one illustrative embodiment of a tactile feedback generationdevice according to the present invention.

FIG. 7 is a general block diagram of a head positioning methodillustrating tactile feedback according to the present invention.

FIGS. 8A-8C show various illustrative embodiments of the general headpositioning method illustrating tactile feedback as shown in FIG. 7.

FIG. 9 is a block diagram of one illustrative embodiment of a handshakeused according to the present invention for determining validity of acommunication link.

DETAILED DESCRIPTION OF THE EMBODIMENTS

FIG. 1 shows a telemetry system 10 according to the present invention.The telemetry system 10 includes implantable medical device 12 andexternal communication device 15 which are operable for establishing acommunication link 16 therebetween. Preferably, the externalcommunication device 15 includes a controller apparatus 32, e.g., aprogrammer apparatus, having a communication head 30 electricallycoupled thereto. The controller apparatus 32 interfaces with theimplantable medical device through the use of the communication head 30,e.g., a programming head or paddle. For ease of use, the programmer head30 is connected to other components of the programmer apparatus 32 via acable, e.g., a straight or coiled cable, although wireless communicationor any other electrical connection is possible.

Generally, the communication head 30 is a hand-held unit adapted to beplaced on or in close proximity to the patient's body over the implantsite of the patient's implanted medical device 12 to establish thecommunication link 16. Preferably, according to the present invention,the communication head 30 includes tactile feedback (also referred toherein as tactile indication) to provide a user with information as tothe proper positioning of the communication head 30 relative to theimplantable medical device 12.

Although the present invention is described herein with respect totactile indication or feedback being provided via the hand-heldcommunication head 30, such tactile indication may be provided to theuser by any other suitable apparatus. For example, the tactile feedbackmay be provided via a device located proximate another portion of theuser's body such as a wearable wristband, an apparatus attachable to auser's pocket or other portions of clothing, or any other apparatuscapable of providing tactile indication to the user. As used herein,tactile indication or tactile feedback refers to any feedbackperceivable by a user's sense of touch, e.g., vibratory motiontransmitted to the housing of the communication head 30 and therefore toa user's hand holding the hand-held communication head 30, or any othermotion perceivable by the user's sense of touch.

As shown in FIG. 1, implantable medical device 12 is implanted in body18. Implanted device 12 includes a housing 13 in which components of theimplantable medical device 12 are hermetically sealed, e.g., pacingcircuitry, defibrillation circuitry, a battery, monitoring circuitry,etc. Also positioned within the housing 13 is transmitter/receivercircuitry 70, as shown in FIGS. 2 and 3. As illustratively shown in FIG.1, at least one lead 14 is connected to the illustrative implantablemedical device 12 in connector block region 17 such as with the use offeedthrough(s) (not shown). For example, the implantable medical device12 may be implanted near a human heart 11. In the case where theimplantable medical device 12 is an illustrative pacemaker implanted inthe body 18, the pacemaker may include a pacing and sensing leadrepresented generally as lead 14 to sense electrical signals attendantto the depolarization and repolarization of the heart 11, and to providepacing pulses for causing depolarization of cardiac tissue in thevicinity of the distal ends thereof.

Implantable medical device 12 may be any implantable medical deviceembodying transmitter/receiver circuitry as described herein. Forexample, in the case where the implantable medical device is apacemaker, the implantable device may be, for example, a pacemaker suchas that described in U.S. Pat. No. 5,158,078 to Bennett, et al.; U.S.Pat. No. 5,312,453 to Shelton et al.; or U.S. Pat. No. 5,144,949 toOlson et al.

Implantable medical device 12 may also be apacemaker-cardioverter-defibrillator (PCD) corresponding to any of thevarious commercially-available implantable PCDs. For example, thepresent invention may be practiced in conjunction with PCDs such asthose described in U.S. Pat. No. 5,545,186 to Olson, et al.; U.S. Pat.No. 5,354,316 to Keimel; U.S. Pat. No. 5,314,430 to Bardy; U.S. Pat. No.5,131,388 to Pless; or U.S. Pat. No. 4,821,723 to Baker, et al.

Alternatively, implantable medical device 12 may be an implantableneurostimulator or muscle stimulator such as that disclosed in U.S. Pat.No. 5,199,428 to Obel, et al.; U.S. Pat. No. 5,207,218 to Carpentier, etal.; or U.S. Pat. No. 5,330,507 to Schwartz, or an implantablemonitoring device such as that disclosed in U.S. Pat. No. 5,331,966 toBennett, et al.

Further, for example, the implanted device 12 may be acardioverter-defibrillator, a brain stimulator, a gastric stimulator, adrug delivery device, a hemodynamic monitoring device, or any otherimplantable device that would benefit from telemetry capabilitiesaccording to the present invention using tactile feedback. Therefore,the present invention is believed to find wide application. As such, thedescription herein making reference to any particular medical device isnot to be taken as a limitation of the type of medical device, which maybe used in association with the tactile feedback of externalcommunication device 15 according to the present invention.

FIG. 2 generally illustrates a high level block diagram of constituentcomponents of one embodiment of implantable medical device 12, where themedical device is implemented with a microprocessor-based architecture.However, the electronic features and operations of the implantablemedical device 12 may be implemented in discrete logic or as amicrocomputer-based system. As shown in FIG. 2, the implantable medicaldevice 12 includes a microcomputer circuit 42 including at least aprocessor 46 and memory 48. The microcomputer circuit 42 is coupled by adata communication bus 50 to a controller circuit 52 of an input/outputcircuit 40. For example, microcomputer circuit 42 may form a customintegrated circuit device augmented by standard RAM/ROM components.

Further, for example, the input/output circuit 40 may include any othernumber of circuits in addition to the controller 52 such as is necessaryfor accomplishing the function of the implantable medical device 12. Forexample, the input/output circuit 40 may include sense amplifiers, peaksense and threshold measurement units, bias circuits, pulse generators,threshold detectors, etc., along with other input/output circuits suchas those required to provide the controller 52 with appropriatesignaling information. The specific embodiments of such circuits are notcritical to the practice of the present invention so long as thecircuits provide for generating signals corresponding to the desiredimplantable medical device and/or are capable of providing controller 52with signals indicative of applicable physiological events, e.g.,natural and stimulated contractions of the heart, and also so long asthe implantable medical device 12 includes transmitter/receivercircuitry 70 according to the present invention for use in a telemetrysystem 10 as described herein.

FIG. 3 is a block diagram of the telemetry system 10 including theimplantable medical device 12 such as described above with reference toFIG. 2 and the external communication device 15. A dashed line 21represents the boundary (e.g., the patient's skin) between the implantedmedical device 12 and external communication device 15.

As described above, the implantable medical device 12 includes at leasttransmitter/receiver circuitry 70 for establishing a communication linkwith external communication device 15. Transmitter/receiver circuitry70, including transmitter circuit 72 and receiver circuitry 70, iscoupled to antenna 19. Although the transmitter/receiver circuitry 70 isshown to include only transmitter circuit 72 and receiver circuit 74,other circuitry for controlling such transmitter and receiver circuits72, 74 also form a part of implantable medical device 12, e.g.,processors for controlling wake-up functions, controlling flow of datato the transmitter for modulation on a carrier signal, etc. In addition,other components of the implantable device 12, e.g., battery, providepower to such circuitry. The antenna 19 may be of any antenna typeutilized in implantable medical device applications for telemetryfunctions, e.g., multi-turn wire coil antennas.

The transmitter/receiver circuitry 70 generates modulated electricalsignals for provision to an antenna 19 such that electromagnetic wavesare radiated. An antenna 64 associated with the communication head 30receives the electromagnetic waves from the implanted medical device 12.Transmitter/receiver circuitry 60 of the external communication device15 receives and demodulates the modulated electrical signals induced inthe antenna 64 representative of the electromagnetic waves radiated fromthe antenna 19 of the implantable medical device 12.

Generally, the external communication device 15 is an apparatus havingat least transmitter/receiver circuitry 60 and an antenna 64 fortransmitting and receiving electromagnetic energy. Further, the externalcommunication device 15 includes control circuitry 80 (e.g., processor,software 84, memory, etc.) connected for control of telemetrytransceiver circuitry 60. The external communication device 15 may beany programmer such as those used in telemetry systems for receivinginformation from an implantable medical device 12 and transmittinginformation thereto. Generally, as previously described herein, suchprogrammers are used to adjust parameters of implantable medical devicesand typically have graphic displays, keyboards, or other user interfacesfor data entry and device control by operator manipulation. Further,such programmers generally include printers or plotters to allow theuser to control, evaluate, and document the extensive capabilities ofthe implanted device 12 from which it is receiving information.

For example, external communication device 15 may include variousdevices available from Medtronic, Inc., assignee of the presentinvention. For example, such devices may include programmers operablewith communication heads available from Medtronic, Inc. such as a 9790programmer operable in conjunction with RF heads including thoseavailable from Medtronic, Inc. under the trade designation 9766 RFHeads, 9766A RF Heads, and 9767 RF Heads; and a Medtronic 2090programmer which is operable with a 9767 RF Head. Further, the devices15 may include patient activators, e.g., patient activated devices forfreezing memory recordings, such as a Medtronic 9462 patient activator;Medtronic 9464 patient activator; or a Medtronic 6190 or 6191 patientactivator. Yet further, the device 15 may be a neurostimulatorprogrammer such as those available under the trade designation Medtronic7432 programmer, Medtronic 3425 programmer, Medtronic 3210 programmer;or a drug delivery device programmer available under the tradedesignation Medtronic 8820 programmer which is operable with a 9766 RFhead. Each of such devices may be modified according to the presentinvention to provide tactile feedback to a user when attempting toestablish a communication link between the implantable medical device 12and the external communication device 15.

The transmitter/receiver circuitry 60 of external communication device15 generates modulated electrical signals for provision to antenna 64 ofthe communication head 30 such that electromagnetic waves are radiated.The antenna 19 associated with the implantable medical device 12receives the electromagnetic waves from the external communicationdevice 15. The transmitter/receiver circuitry 70 of the implantablemedical device 12 receives and demodulates the modulated electricalsignals induced in the antenna 19 representative of the electromagneticwaves radiated from the antenna 64 of the external communication device15.

As would be known to one skilled in the art, the transceiver circuitry60 of the external communication device 15 includes receiver circuitry62 that is compatible with the transmitter 72 of the implanted medicaldevice 12 and operable for receiving and demodulating the transmittedsignal therefrom. Further, the transceiver circuitry 60 of externalcommunication device 15 includes transmitter circuitry 61 that iscompatible with the receiver 74 of the implanted device 12 and operablefor generating a modulated signal of which the receiver of the implantedmedical device 12 is capable of receiving and demodulating. Thetransceiver circuitry 60 is coupled to antenna configuration 64 forcommunicating with the implantable medical device 12 via antenna 19.

Antenna 64 is preferably disposed within hand-held communication head 30surrounded by a housing 31 generally represented by dashed line in FIG.3. The hand-held communication head 30 can then be conveniently placedin proximity to the patient's implant site. When so positioned, antenna64 receives uplink telemetry signals transmitted from implanted medicaldevice antenna 19 and transmits downlink telemetry signals to bereceived by implanted medical device antenna 19 as indicated by thedouble-arrowed communication link 16.

It will be readily apparent to one skilled in the art from thedescription herein that the present invention need not be used as abi-directional telemetry system, but may be used as a unidirectionalsystem. In other words, external communication device 15 may onlyinclude a receiver to receive information from a transmitter ofimplantable medical device 12. For example, this may be the case in animplantable monitoring device. Likewise, external communication device15 may only include a transmitter for transmitting information to areceiver of the implantable medical device 12. This may be the casewhere implantable medical device 12 is only being programmed by theexternal communication device 15.

To provide feedback as to the proper positioning of the communicationhead 30 relative to the implanted medical device antenna 19 to establisha valid communication link, tactile feedback generation device 90 isprovided according to the present invention. Unlike conventionalindicator devices, tactile feedback generation device 90 allows a userto locate an implantable medical device 12 using the communication head30 without the requirement of looking at an indicator light. However, asfurther described below, other indicators may be used in conjunctionwith the tactile feedback generation device 90. For example, a positionindicator or telemetry status indicator 86 may be used in conjunctionwith the tactile feedback to properly position the external antenna 64relative to the implanted medical device antenna 19, e.g., the telemetrystatus indicator may be activated after a handshake is performed andconfirmation thereof is attained indicating that at a validcommunication link has been established at a certain communication headposition, while tactile feedback may be used to indicate a more optimalposition for the communication head 30.

The use of tactile feedback in positioning the communication head 30 forperforming telemetry according to the present invention shall be firstgenerally described with reference to the general head positioningmethod 100 of FIG. 7 and then various illustrative embodiments of such ageneral method shall be described with reference to FIGS. 8A-8C. Headpositioning method 100 generally includes the initiation of a telemetrysession as shown in block 102. For example, a telemetry session may beinitiated by the closing of a reed switch of an implantable medicaldevice 12 as is known in the art, may be initiated by a wake-up pulse,or may be initiated by any other technique for beginning a telemetrysession. Thereafter, telemetry is attempted (block 103) under control ofcontrol circuitry 80. It is then determined whether valid telemetry hasbeen accomplished (block 104) or, in other words, whether a validcommunication channel or link is established between the implantablemedical device 12 and the external communication device 15. If such avalid telemetry link is not determined, then no tactile feedback isprovided to the user. As such, the user knows that the usercommunication head 30 must be moved relative to the implanted device 12.Further communication between the implantable medical device 12 and theexternal communication device 15 is then attempted with thecommunication head 30 in a new position. Once valid telemetry isachieved, tactile feedback is activated (block 106) based on thetelemetry validity determination (block 104).

One skilled in the art will readily recognize that various techniquesmay be used for determining valid telemetry (block 104). For example,valid uplink telemetry may be determined, valid downlink telemetry maybe determined, bi-directional valid telemetry may be determined, signalstrength may be used for determining valid telemetry, handshaking may beused to determine valid telemetry, CRC checking or error checking may beused to determine valid telemetry, or any other processes or combinationof processes for determining that a channel is valid may be usedaccording to the present invention.

Further, one skilled in the art will recognize that tactile feedback maybe used in different manners to indicate valid telemetry under differentcircumstances or different applications. For example, tactile feedbackmay be used upon initial detection of a valid communication channel eventhough the communication head may not be at a position that provides asignal of optimum strength; tactile feedback may be used only uponfinding a communication head position that provides a telemetry signalof a particular strength as determined by a predetermined referencestrength level; tactile feedback may be used to indicate an initialdetection of a valid communication channel with the tactile feedbackbeing modified as a function of signal strength as positions providinggreater or lesser signal strength are located; etc.

FIGS. 8A-8C are provided to illustrate several embodiments of thegeneral head positioning method 100 described above with reference toFIG. 7. As shown in FIG. 8A, head positioning method 120 includestelemetry initiation (block 121). For example, as described above, atelemetry session may be initiated by the closing of a reed switch of animplantable medical device 12 as is known in the art, may be initiatedby a wake-up pulse, or may be initiated by any other technique forbeginning a telemetry session. Thereafter, telemetry is attempted (block123) such as by starting a handshake protocol. For example, afterinitiation of the telemetry session (block 121), a handshake sequencemay be periodically performed to establish and/or continually assess avalid telemetry link.

Generally, the handshake protocol includes carrying out a handshakesequence that includes a handshake request, a window of time for aresponse to the request, and a handshake confirmation. One skilled inthe art will recognize that either the implantable medical device 12 orthe external communication device 15 may be used to initiate thehandshake sequence with a handshake request. Preferably, the handshakesequences are initiated by a handshake request from the implantablemedical device 12. For example, the handshake protocol may be performedin a manner such as that described in U.S. Pat. No. 5,292,343 toBlanchette, et al., entitled “Handshake for Implanted Medical DeviceTelemetry.”

FIG. 9 shows one illustrative embodiment of a handshake procedure 246which may be used in conjunction with the telemetry system 10. Oneskilled in the art will recognize that various handshake sequences andtechniques may be used to determine a valid communication channelbetween the implantable medical device 12 and the external communicationdevice 15. As such, the present invention is not limited to anyparticular handshake sequence or technique. It will be furtherrecognized that handshake sequences are periodically carried out duringan initiated telemetry session to determine that a link is still validas well as at the beginning of a telemetry session to determine theestablishment of a valid communication channel.

As shown in FIG. 9, the illustrative handshake procedure 246 isinitiated at handshake block 148. The implantable medical device 12transmits the handshake request (block 250). If the externalcommunication device 15, e.g., programmer, receives the handshakerequest as determined at block 252, then external communication device15 (e.g., programmer) transmits a handshake reply (block 253) during ahandshake reply window. If the programmer 15 does not receive thehandshake request, a time-out period is issued so as to continue waitingfor the handshake request (block 255). If, during the time-out, externalcommunication device 15 receives a handshake request, a handshake reply(block 253) is issued. Block 256 illustrates that some time during thetime-out is expended by the implanted medical device 12 in waiting forthe handshake reply. If during the time-out no handshake reply isreceived by the implanted medical device 12 indicating that thehandshake request was not received by external communication device 15,a handshake failure (block 258) is issued and the handshake sequence isexited (block 260) until the next periodic handshake sequence. Aproperly timed reply during the reply window from the externalcommunication device 15 received by the implantable medical device 12(block 254) causes transmission of a handshake confirmation (block 262).

As shown in FIG. 8A, upon completion of the handshake sequence, if aconfirmation was not received, then further communication is attempted,e.g., another handshake is attempted (block 123). On the other hand, ifthe handshake is confirmed (block 122), then optionally, a visual oraudible indicator is provided (block 126) and, according to the presentinvention, tactile feedback may be also activated (block 124). Theoptional indication shown by block 126 in FIG. 8A is also illustrated inFIG. 9. For example, as shown in FIG. 9, upon receipt of theconfirmation (block 264) by the external communication device 15, anindication that a link is established may be provided, e.g., an LED isextinguished (block 266). Likewise, an indication that the confirmationwas not received may also be indicated in some manner, e.g., an LED islighted (block 268). Thereafter, the handshake sequence is exited (block270).

Although tactile feedback may be provided in response to a confirmedhandshake as described above which indicates a valid communicationchannel to the user, tactile feedback may be inhibited until adetermination has been made that the telemetry signal strength meets apredetermined reference level. This determination is further describedbelow with reference to FIG. 8B.

Further, as shown in FIG. 8A, in addition to the activation of tactilefeedback upon confirmation of a valid handshake, the tactile feedbackmay be adjusted as a function of the telemetry signal strength (block124). The signal strength (block 128) is provided such that the tactilefeedback may be activated as a function thereof. For example, thefrequency of vibration may be increased as signal strength (block 128)is increased. Likewise, the frequency of vibration of the tactilefeedback may be decreased upon a decrease in signal strength (block128). In such a manner, the user is provided with a varied tactilefeedback as a function of the signal strength such that optimumpositioning of the head 30 can be attained by the user. For example, theuser may move the handheld communication head 30 to the position wheretactile feedback having the high frequency of vibration is sensed. Withthe communication head 30 properly positioned, telemetry is completed(block 129).

Signal strength may be determined by any number of different techniques.Such signal strength may be representative of uplink signal strength,downlink signal strength, or a combination of uplink and downlink signalstrength. For example, when uplink telemetry signals are received byantenna 64 and uplink receiver 62, the strength of the received signalscan be assessed or monitored based upon the gain setting of the uplinkreceiver 62. Such monitoring of the gain is, for example, described inU.S. Pat. No. 5,107,833 to Barsness and U.S. Pat. No. 5,324,315 toGrevious. Generally, the gain of the uplink receiver 62 is inverselyproportional to the signal strength. For example, a lesser signalstrength results in a higher gain being provided by the receiver 62, anda higher signal strength results in a lesser gain being provided byreceiver 62.

FIG. 8B illustrates another alternate embodiment of a head positioningmethod 130. The head positioning method 130 includes initiatingtelemetry (block 131) in a like manner as described with reference toFIG. 8A. Likewise, as shown in block 133, telemetry is attempted and ahandshake sequence 132 is performed. Upon confirmation of the handshake(block 132), a telemetry status indication may be optionally provided tothe user (block 135), e.g., telemetry status indicator 86 as shown inFIG. 3 is activated.

Thereafter, upon confirmation of the handshake (block 132), signalstrength (provided as described previously with reference to FIG. 8A)based on gain of the uplink receiver 62 is compared to a referencethreshold. Such a comparison may be accomplished in any number ofmanners, and is not limited to any particular comparison circuit. Ifsuch a reference threshold is not met, then the user is not providedwith tactile feedback and the user recognizes the need to change theposition of the communication head 30. Further attempts to performtelemetry are then carried out (block 133). However, if the telemetrysignal strength satisfies, e.g., is greater than, the referencethreshold (block 134), then tactile feedback is activated (block 136)indicating to the user that a valid communication channel isestablished.

Thereafter, optionally, according to this embodiment, the tactilefeedback may be deactivated (block 138) after a predetermined time eventhough a valid communication channel still exists between theimplantable medical device 12 and the external communication device 15,i.e., the telemetry signal strength satisfies the reference thresholdrequirements. However, as described previously, handshake sequences arestill carried out periodically and continuously evaluate whether thelink continues to be valid over time. If a handshake sequence is notconfirmed after the tactile feedback has been deactivated (block 138),the communication link is no longer valid (block 140) and an alarmindicator (block 144) is activated to indicate to the user that the usermust reposition the communication head 30 (block 146) such that a validcommunication link can be re-established. If, however, continualconfirmation of the handshakes are completed, the user understands thatthe link is still valid and communication continues until telemetry iscompleted (block 142).

Another illustrative alternate embodiment of a head positioning method150 is shown in FIG. 8C. In this embodiment, after a telemetry sessionis initiated (block 151), telemetry is attempted (block 153). However,in this particular embodiment the signal strength based on the gain ofthe uplink receiver 62 is compared to a predetermined thresholdreference (block 152). If the signal strength is greater than thepredetermined threshold reference, then tactile feedback is activated(block 154) and the valid telemetry can be performed. However, if thesignal strength is not greater than the predetermined threshold, thenthe user must move the communication head 30 to another positionrelative to the implanted medical device 12 such that further telemetrymay be attempted (block 153) and further comparisons of signal strengthto a threshold can be carried out until the signal strength is greatenough to activate tactile feedback (block 154) such that the user knowsthat a valid communication channel is established between theimplantable medical device 12 and external communication device 15.

One skilled in the art will recognize that the implementation ofproviding tactile feedback to a user may be performed under the controlof software 84 of control circuitry 80 of the external communicationdevice 50 as shown in FIG. 3. As such, various techniques of using thetactile feedback can be implemented, including but clearly not limitedto controlling when tactile feedback is provided to a user based on anynumber of factors such as signal strength, error detection, cyclicredundancy checking, handshake confirmation, etc. For example, thedetermination of a valid channel using a handshake sequence may be usedalone or in combination with the use of signal strength to initiatetactile feedback, and signal strength may be used alone to determine thevalidity of the channel as compared to use of a handshake sequence.

Further, one skilled in the art will recognize that these illustrativeembodiments of determining the validity of the communication channelbetween the implanted medical device 12 and the external communicationdevice 15 are given for illustration only and that there are variousother methods which may be used to determine a valid communicationchannel. The present invention is not limited to any particular validitydetermination method but is limited only to the use of tactile feedbackto assist the user in positioning the communication head 30 relative tothe implanted medical device 12 such that when a valid communicationchannel has been determined the user is effectively notified.

A more detailed diagram of one illustrative embodiment of a portion ofan external communication device 300 for carrying out tactile feedbackfor positioning of a communication head according to the presentinvention is shown in FIG. 4. The external communication device 300includes communication head 330 electrically connected to controlcircuitry 384. The communication head 330 includes therein an antenna364 coupled to transceiver circuitry 360 including downlink transmitter361 and uplink receiver 362. Generally, the uplink receiver 362 includesan automatic gain control amplification stage (not shown), whichprovides for adjustment in gain based on signal strength, e.g., uplinkand/or downlink signal strength. A signal representative of the gain isprovided to a log amplifier 370, which provides as an output thereof asignal representative of the log of the signal strength. The log of thesignal strength is compared to a reference strength 373 as generallyillustrated by comparator circuitry 372. The tactile feedback generationdevice 374 is controlled by comparator circuitry 372. The comparatorcircuitry 372 has applied thereto a threshold reference 373, which isused for the comparison to the output of log amplifier 370representative of the gain of uplink receiver 362, and has appliedthereto an optional status indication 378.

Optional status indication 378 is controlled via controller circuitry384, which is also used in controlling the handshake between theexternal communication device 300 and an implantable medical device 12.When valid telemetry is detected per the handshake, optional statusindication 378, e.g., an LED, may be used to indicate to the user that atelemetry channel has been validated. Further, an enable signal isprovided to the comparator circuitry 373 upon occurrence of a confirmedhandshake such that only if the handshake is confirmed can tactilefeedback be performed. As such, even if the handshake is confirmed, itis not certain that the placement of the communication head 330 isoptimum for the telemetry link. Therefore, the log of the strengthsignal output from log amplifier 370 is provided to comparator circuitry372 for comparison to a threshold level 373. In this embodiment, onlyupon the strength signal meeting the threshold reference 373 is tactilefeedback device 374 activated.

It will be recognized that various threshold levels may be used forcomparison with the output of the log amplifier 370 such that variousoptional indication devices 376 may be activated. For example, and asfurther described below with reference to FIG. 5, an array of LEDs maybe used to visually indicate to a user the strength of the telemetrysignal. Likewise, the tactile feedback generation device 374 may becontrolled by the strength signal, e.g., the frequency of vibration ofthe tactile feedback generation device 374 may be varied according tothe strength of the telemetry signal.

FIG. 5 shows one illustrative embodiment of a portion of an externalcommunication device 400 similar to that of FIG. 4 showing the use of anarray of LEDs 474 in combination with tactile feedback. As showntherein, the log amplifier 470 receives as its input a signalrepresentative of the gain of the uplink receiver and provides an outputrepresentative of the log of the signal strength to driver circuitry472. Driver circuitry 472 is configured to drive an array of LEDs 474 asa function of the signal representative of the log of the signalstrength output from the log amplifier 470. For example, with a lowerstrength signal, only a single LED of the array 474 may be lit while asthe strength signal is increased, more LEDs may be lit.

As further shown in FIG. 5, tactile feedback generation device 476 maybe coupled to any point of the LED array such that tactile feedback maybe provided to the user by the generation device 476 upon activation ofa certain number of LEDs of the array 474. For example, it may bedesired that tactile feedback be provided to the user upon illuminationof three LEDs corresponding to a certain signal strength.

The tactile feedback generation device 90, as shown in FIG. 3, and thetactile feedback generation devices as described with reference to theother figures, may be provided in any number of manners. For example, asshown in FIG. 6, tactile feedback generation device 90 is provided bycontrol of a vibrating motor 91, which is mechanically coupled to thehousing 31 of the communication head 30 so as to impart motion orvibration to the communication head 30. For example, various vibratingmotors have been used in the paging industry such as described in U.S.Pat. No. 4,794,392 to Selinko, entitled “Vibrator Alert Device for aCommunication Receiver.” The vibrating motor 91 is controlled by acontrol signal 92 applied to a voltage regulator 93 which turns thevibrating motor 91 on and off. When the vibrating DC motor begins tovibrate, the user is provided with information regarding the positioningof the communication head 30 relative to the implanted medical device 12as described herein.

It will be recognized that other forms of generating tactile feedbackmay also be used. For example, piezoelectric devices may be activated toprovide for vibration, an electric solenoid may be activated forproviding vibration, or a relay contact may be chattered to also providefor vibratory or tactile feedback. As such, one skilled in the art willrecognize that any number of vibration devices may be employed inaccordance with the present invention such that tactile feedback may beused to indicate the validity of a communication channel between theexternal communication device 15 and the implanted medical device 12.

All patents and references cited herein are incorporated in theirentirety as if each were incorporated separately. This invention hasbeen described with reference to illustrative embodiments and is notmeant to be construed in a limiting sense. As described previously, oneskilled in the art will recognize that various other illustrativetechniques for using tactile feedback in the positioning of acommunication head relative to an implantable medical device may beimplemented according to the present invention. Various modifications ofthe illustrative embodiments, as well as additional embodiments of theinvention, will be apparent to persons skilled in the art upon referenceto this description.

1. An implantable medical device telemetry method, the method comprisingthe steps of: providing an implantable medical device, the implantablemedical device including at least one of a device transmitter and adevice receiver; providing an external communication device, theexternal communication device including at least one of an externaltransmitter and an external receiver connected to an antenna forcommunication with the at least one of the device transmitter and thedevice receiver; determining validity of a communication link betweenthe at least one of the device transmitter and the device receiver ofthe implantable medical device and the at least one of the externaltransmitter and the external receiver of the external communicationdevice; and providing a tactile indication as a function of the validitydetermination.
 2. The method of claim 1, wherein the externalcommunication device includes a user communication head movable relativeto the implantable medical device when the implantable medical device isimplanted, and further wherein providing the tactile indication includesproviding tactile indication to a user via the user communication head.3. The method of claim 1, wherein determining validity of thecommunication link includes: detecting communication of a signal betweenthe at least one of the device transmitter and the device receiver ofthe implantable medical device and the at least one of the externaltransmitter and the external receiver of the external communicationdevice; determining the strength of the communicated signal; andcomparing the strength of the communicated signal to at least onepredetermined reference strength.
 4. The method according to claim 3,wherein providing a tactile indication includes controlling thefrequency of vibration of the tactile indication as a function of thestrength of the communicated signal.
 5. The method of claim 1, whereindetermining validity of a communication link includes: completing ahandshake between the at least one of the device transmitter and thedevice receiver of the implantable medical device and the at least oneof the external transmitter and the external receiver of the externalcommunication device.
 6. The method of claim 1, wherein providing thetactile indication as a function of the validity determination includesinitiation of the tactile indication upon determination of a validcommunication link.
 7. The method of claim 6, wherein providing thetactile indication as a function of the validity determination furtherincludes discontinuing the tactile indication after a predeterminedperiod of time following initiation thereof.
 8. The method of claim 7,wherein providing the tactile indication as a function of the validitydetermination further includes activation of an indicator when the validcommunication link becomes invalid following discontinuation of thetactile indication.
 9. The method of claim 1, wherein providing thetactile indication as a function of the validity determination includescontinuously providing tactile indication during the entire period oftime that a valid communication link is determined.
 10. The method ofclaim 1, wherein the external communication device includes aprogramming apparatus for the implantable medical device.
 11. The methodof claim 1, wherein the external communication device includes a patientactivation apparatus for the implantable medical device.
 12. The methodof claim 1, wherein providing an implantable medical device includesproviding an implantable device selected from a pacemaker, acardioverter/defibrillator, a brain stimulator, a neurostimulator, amuscle stimulator, a gastric stimulator, an implantable monitor, ahemodynamic monitor, a pacemaker/cardioverter/defibrillator, and a drugdelivery device.
 13. An implantable medical device telemetry method, themethod comprising the steps of: providing an implantable medical device,the implantable medical device including at least one of a devicetransmitter and a device receiver; providing an external communicationdevice including a movable head apparatus including at least an antennatherein connected to at least one of an external transmitter and anexternal receiver for communication with the at least one of the devicetransmitter and the device receiver; moving, by a user, the movable headapparatus relative to the implantable medical device; and providingtactile feedback to the user via the movable head apparatus uponmovement of the movable head apparatus to a position where informationbetween the at least one of the device transmitter and the devicereceiver of the implantable medical device and the at least one of theexternal transmitter and the external receiver of the externalcommunication device is communicated.
 14. The method of claim 1, whereinproviding tactile feedback to the user via the movable head apparatusincludes determining validity of a communication link and providing thetactile feedback to the user as a function thereof.
 15. The method ofclaim 14, wherein determining validity of a communication link includes:detecting the communication of a signal between the at least one of thedevice transmitter and the device receiver of the implantable medicaldevice and the at least one of the external transmitter and the externalreceiver of the external communication device; determining a strength ofthe communicated signal; and comparing the strength of the communicationsignal to at least one predetermined reference strength.
 16. The methodof claim 15, wherein providing the tactile feedback includes controllingthe frequency of vibration of the tactile feedback as a function of thestrength of the communicated signal.
 17. The method of claim 14, whereindetermining validity of a communication link includes completing ahandshake between the at least one of the device transmitter and thedevice receiver of the implantable medical device and the at least oneof the external transmitter and the external receiver of the externalcommunication device.
 18. The method of claim 14, wherein providingtactile feedback includes initiation of the tactile feedback upondetermination of a valid communication link and discontinuing thetactile feedback after a predetermined period of time following suchinitiation.
 19. The method of claim 18, wherein providing the tactilefeedback further includes activation of an indicator when the validcommunication link becomes invalid following the discontinuation of thetactile feedback.
 20. The method of claim 14, wherein providing thetactile feedback includes continuously providing tactile feedback duringthe entire period of time that a valid communication link is determined.21. The method of claim 13, wherein providing the external communicationdevice includes providing a programming apparatus for the implantablemedical device.
 22. The method of claim 13, wherein providing theexternal communication device includes providing a patient activationapparatus for the implantable medical device.
 23. The method of claim13, wherein providing an implantable medical device includes providingan implantable device selected from a pacemaker, acardioverter/defibrillator, a brain stimulator, a neurostimulator, amuscle stimulator, a gastric stimulator, an implantable monitor, ahemodynamic monitor, a pacemaker/cardioverter/defibrillator, and a drugdelivery device.